Funding is requested for a FACSVantage SE cell sorter for the UCLA Flow Cytometry Core Facility (FCCF) established in 1988. Under the Direction of Dr. Beth D. Jamieson and the Supervision of Ingrid Schmid the FCCF provided sorting services in the last year for 32 investigators from UCLA and neighboring institutions. The FCCF is supported by user fees and direct grants from the Johnson Comprehensive Cancer Center and the UCLA AIDS Institute. Secure funding for the facility is available until 2003. The requested instrument will replace an 11-year old FACStar plus that lacks the technological capabilities required by FCCF users. Unlike the FACStar plus the FACSVantage SE is equipped with: non-rectangular sort gates, enhanced sorting electronics for increased sort recoveries, digital processing for increased fluorescence sensitivity, fluorescence compensation across all detectors and laser beams, four-way sorting, TurboSort for increased sorting speed, Aerosol Management for biohazardous sorts, and the Automated Cell Deposition Unit for sorting of cells into single wells. These are features that UCLA investigators have indicated as critical for the progress of their research. To meet the high percentage of patient and donor sorts that are difficult, or impossible, to schedule, the FCCF has maintained two sorters since 1991. The demand for updated equipment was so critical that UCLA donated funds that, together with accrued users fees, were used to replace one sorter with a used FACS Vantage SE. However, funds were only sufficient to purchase a used instrument lacking some of the needed technology. The FCCF is in danger of losing the use of the remaining FACStarplus due to aging instrument components that cannot be replaced or up-graded. Should this occur, many projects would be impeded or made impossible. The requested instrument will relieve the deficiencies of the current instruments and accommodate the excess workload. The FACS Vantage is requested as a shared instrument to support a variety of research projects including, but not limited to: I) analysis of latent reservoirs for HIV-1; ii) characterization of the role of HIV-1 vpr in infection and pathogenesis; iii) development of Lentivirus-based gene therapy vectors; iv) analysis of the function of CD4 expression on CD8+ T-cells; v) characterization of differences between adult and fetal thymocyte development; vi) studies into the impact of hormones on B cell differentiation; vii) investigation of early T-ceIl lineage commitment; viii) investigation of the regulation of stem cell differentiation and identification of immature human lymphoid progenitors in bone marrow. The FCCF has a remarkable record of developing novel methods and protocols and for establishing guidelines for sorting of biohazardous samples. The FCCF staff will continue to develop and adapt novel technologies for use with the new instrument to support UCLA investigators in their efforts to remain on the cutting edge of science.